This invention relates generally to apparatus for enabling a production line to maintain a constant output. More particularly, the invention relates to accumulator apparatus which gathers articles during the time when a downstream machine is inoperative, and automatically feeds such articles back into the production stream when the downstream machine resumes production.
Multi-stage production lines must allow for situations in which one stage of the line is inoperative, but other stages are capable of continued operation. Lacking such provision, the entire line would cease operation every time a single component experienced and interruption. Obviously, that situation is intolerable. The need, therefore, can be expressed in general terms as the requirement to provide for a reservoir. or accumulation, between downstream and upstream stages of operation. When the upstream stage is inoperative, the reservoir receives output from the downstream stage, allowing that stage to continue operation. When the downstream stage is inoperative, similarly, the reservoir supplies the downstream stage with input, allowing that stage to continue operation. By alternately absorbing and supplying articles, the reservoir allows for interruptions in the operation of individual components without shutting down the entire production line.
Industries concerned with handling rectangular-shaped, relatively small articles--such as the cigarette industry--have met this need in a number of ways. The most common solution is to provide apparatus which stacks output from a downstream machine into a vertical magazine; stored articles are then manually unloaded and fed back into the production stream. The requirement for manual unloading obviously is undesirable, as it necessitates high labor costs and slows down production. Additionally, such accumulators have limited capacity and thus can be overloaded easily.
This problem is manifested, of course, at several stages in the manufacturing process for cigarettes. Between the cigarette packaging machine (which wraps cigarettes in paper and foil packages) and the cartoning machine (which places packages within cartons, generally at ten packages per carton), a solution to the accumulation problem is presented by Seragnoli, U.S. Pat. No. 3,360,100. When the downstream (cartoning) machine is interrupted, this mechanism accumulates packages by lifting packs upward into a vertical magazine through the operation of a plunger. When the downstream machine resumes operation, the accumulator holds the packages thus inserted until the upstream (packaging) machine is interrupted, whereupon it discharges packages toward the downstream machine until the upstream machine resumes operation.
Devices such as that disclosed by Seragnoli, however, leave two problems unsolved. First, production time lost during interruption of the downstream machine cannot be made up. That is, no provision exists in the prior art for combining the output of an accumulator with the output of the upstream machine to increase throughput after the downstream machine resumes operation. The downstream machine can be supplied either from the accumulator or from the upstream machine, but not from both. Second, such devices assume that the upstream and downstream machines will be interrupted for approximately equal times. The accumulator can be emptied only during interruptions of the upstream machine; thus, if the upstream machine in fact is less prone to malfunction than is the downstream machine, there will be a net addition to the accumulator. At some point, the accumulator will be filled to capacity, requiring a deliberate stoppage of the upstream machine in order to empty the accumulator at least partially.
At the stage of cigarette manufacturer between the cartoning machine and the casing machine (which loads cartons into cases for shipment), these problems present serious drawbacks to use of the Seragnoli-type device. First, the throughput of the casing apparatus is greater than that of the cartoning machine; thus, if such apparatus were available, the casing apparatus could accept input from both an accumulator and from the cartoning machine, allowing for lost production time to be made up. Second, the casing machine and its associated conveyor apparatus are in fact more prone to downtime than is the cartoning machine. Thus, an accumulator rapidly would fill to capacity.
The need still exists, therefore, for an accumulator capable not only of receiving articles from an upstream machine and discharging articles to a downstream machine, but also capable of merging its output into a continuing stream of articles. It is that need to which the present invention is addressed.